Position indicator switches



Dec. 31, 1968 D, STEWART 3,419,691

POSITION INDICATOR SWITCHES Filed NOV. 23, 1965 Sheet Of 2 was.

' INVEYTOR DAV/D S'TEWAKT Dec. 31, 1 968 0. STEWART 3,419,691

POSITION INDICATOR SWITCHES Filed Nov. I 23,- 1966 INVENTOR. ZMV/D .S'EWART United States Patent 0 3,419,691 POSITION INDICATOR SWITCHES David Stewart, Bellevue, Wash., assignor to The Boeing Company, Seattle, Wash., a corporation of Delaware Filed Nov. 23, 1966, Ser. No. 596,684 3 Claims. (Cl. 200-6152) This invention relates to improvements in circuit breakers and more particularly to a tilt-actuated circuit breaker, the contacts of which open upon tilting, with respect to a reference plane, of the carrier member supporting the circuit breaker. Such a carrier member may include the landing gear truck of modern aircraft.

Failure of many prior art circuit breaker switches to function properly was due to short circuits arising from the accumulation of water within a supposedly airtight or sealed switch case. Any air leak passageway into typical sealed switch cases acts as a water trap. Sources of such water traps are imperfect soldering techniques and the unpredictable life of the switch actuator shaft seal.

Later switch designs have abandoned the sealed or airtight approach and have introduced a vented case concept. This, too, has proved unsatisfactory; the vent typically does not clean itself of dust particles and is open to water ingestion when the switch case is subject to water environments; insulation material used in many of the vented switch cases is water absorbent. Such insulation reduces electrical insulation, promotes tracking and causes switch contact arms to hang up.

It is an object of the teachings of this invention to provide a vehicle tilt-actuated switch having no life limiting factors built into it. The switch is designed to last indefinitely, requiring only occasional cleaning and inspection.

A further object of the teachings of this invention is to provide a circuit breaker switch capable of handling contaminating environments to which it is subjected. Contaminants which ordinarily cause short circuit problems include water, cleaning solutions and oil. A feature of the teachings of this invention provides that should such contaminants as sand or dust acquire entrance into the switch case, no failure of the switch will arise.

A further object of the teachings of this invention is to provide means for eliminating, as far as possible, all bearings and pivots so that working parts will be as few and simple as possible.

Briefly, the teachings of this invention are directed to an improvement in vehicle position actuator switches. The switch is essentially comprised of a plurality of movable electrical contacts, ie, two support members, each carrying two physically separated electrical contact elements. The electrical contacts are disposed to move relative to one another in response to actuator means. More particularly, the support arms or members are adapted to move in a parallel, longitudinally reciprocating manner, the two contact elements of each arm being separated by an insulation means. The contact arms are a portion of a mated Z configuration. The insulation means are so disposed that when the vehicle tilts, relative to a reference plane, the actuator means allows said contact arms to move and the contact elements thereon to slide apart on said insulation means to an open switch position. The open position of the switch occurs when the vehicle tilts, the insulation means sliding across the opposite contact element of the adjacent contact arms, thereby latching the contact means in an open position. The insulation means therefore acts as a cam in holding the circuit open under tilting conditions, and as an insulator and a cleaning agent for removing contaminants as the insulation means slides over the contact surfaces. A ventilation assembly is provided in combination with the container means which encloses the switch. The ventilation assembly allows for the circulation of air within the switch casing and is constructed in the form of a labyrinth to prevent dust or foreign particles having mass from reaching the interior of the switch casing.

The switch finds particular utility on the truck assembly of aircraft. The truck beam must bear a definite angle relationship to the landing gear strut or aircraft structure. Any tilting of the truck assembly will activate the switch of this invention to open and provide the pilot with a signal indication. The signal indication serves to advise the pilot when the truck assembly leveling mechanism has failed to work. In this case, danger exists that the aircraft wheels will catch on aircraft structure during landing gear retraction or lowering. Total failure of the landing gear to lock down could then occur and result in serious accidents.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings, showing by way of example the preferred embodiment of the invention.

In the drawings:

FIGURE 1A is a cutaway perspective of a vehicle position or tilt actuated level switch according to the teachings of this invention;

FIGURE 1B is a section view of the vehicle tilt actuated level switch according to the teachings of this invention;

FIGURE 1C is a side elevation view of the vehicle tilt actuated level switch showing the actuator mechanism for the switch.

FIGURE 2 shows the movable electrical contact means in the closed switch position;

FIGURES 3A and 3B show the movable electrical contact means in the open switch position.

FIGURE 4 represents an assembly detail of the actuator switch according to the teachings of this invention;

FIGURE 5 represents a section view of an alternate embodiment of the teachings of this invention.

Referring to the drawings, FIGURE 1A shows a perspective view of a vehicle tilt actuated switch 10, according to the teachings of this invention. Metal casing means 12 encloses the switch mechanism described below in detail. As seen in FIGURE 1B, attachment means 14 are shown in combination with the casing means 12. The attachment means 14 may be simply cylindrical sleeves through which bolts (not shown) attach the switch 10 to a vehicle support structure in a reference plane position, e.g., horizontal or vertical or some number of degrees from horizontal. Electrical outlet 16 is attached to the casing means 12 by means (not shown) such as soldering. Electrical leads 15 interconnect the outlet 16 with movable support arms 18. Integrally connected to the arms 18 are contacts 21 and insulation means 22.

The arms 18 are made so that they will spring outwards toward the casing 12 when they are installed. The arms 18 are restrained in the closed circuit condition of FIGURE 1B by the outward extension 24 of spring means 26, as clearly seen in FIGURE 1A. Spring 26 is so designed that under non-tilt conditions the extension 24 biases the contact arms 18 in a closed circuit condition, i.e., with physical contact existing between contact elements 21 and between a further electrical contact junction formed between fixed stop 21A, welded to casing 12, and arms 18 (as seen in FIGURE 1B). By using two arms 18 instead of two pivoted levers, pivot friction or possible seizure at pivot points has been eliminated.

In FIGURES 2, 3A and 3B, insulation means 22 (such as a cylindrical Teflon sleeve) is shown located between the individual contact elements 21 on each contact arm 18. The insulation means 22 serves as an insulator in the open switch condition and also wipes clean the contact 3 points 21 as the switch goes from the open circuit condition of FIGURES 3A and 3B to the closed circuit condition of FIGURE 2. FIGURES 3A and 3B show the switch in an open circuit condition. The insulation means 22 are shown serving as an insulator, a cam and as a contact 21 cleaner.

Thus, continuing with reference to FIGURES 2, 3A and 3B the switch 10 is essentially comprised of two contact arms 18 each carrying two physically separated contact elements 21 collectively comprising sets of contacts adapted to move in a parallel longitudinally reciprocating manner with the arms 18, the two contact elements 21 of each arm 18 being separated by insulation means 22. The arms 18 are essentially a portion of a mated Z configuration. A third electrical contact exists between fixed contact 21A, fixedly attached to casing 12 by means such as welding. This latterelectrical contact is open when a limit of mechanical travel is reached by arms 18, i.e., when one of the arms 18 is against fixed stop 47, also attached to casing 12 by means such as welding. Separation of the two sets of contact elements 21, attached to the two arms 18, also occurs upon vehicle tilting, the insulation material 22 sliding across the opposite contact element 21 of the adjacent set of contact elements 21, thereby latching the contacts 21 in an open circuit condition. Upon vehicle tilting, separation between arms 18 and fixed contact 21A occurs before separation of contact elements 21. Thus an early signal indication is given before tilting reaches such a serious degree that exists when contacts 21 have separated. A plurality of contacts are used in parallel so as to distribute the electrical load and -minimize arcing upon break or make of said contacts.

A switch 10 actuator means 28 will be fully described with reference to FIGURE 4. As shown in FIGURES 1A and 1B, a pair of earns 30 are positioned between the extension 24 of spring 26. The angle setting a, best seen in FIGURE 2, between the two cams 30 controls the switch dead band, i.e., the amount of tilt the vehicle is allowed before restraining arms 24 are moved aside by the cams 30, as in FIGURES 3A and 3B, allowing the arms 18 to spring apart. The relation between cams 30 and the external drive lever 31, as seen in FIGURES 1C, 2 and 4, defines the neutral position. When the cams 30 are positioned on shaft 32 at a desired angle, nut 34, as seen best in FIGURE 4, is tig htened down upon shaft 32 forcing cams 30 tightly together up against shaft 32 flange 29. Locking provision is made by drilling a cotter pin hole 36 in the nut 34, through both cams 30 and into the flange 29.

Shaft 32 is rotatably supported within casing 12 by a bushing 37. Bushing 37, made of plastic material, is attached to a bracket 38 by any convenient means. Bracket 38 is mounted within casing 12 by bolts 40. The arms 18 are attached to bracket 38 by screws 43. A cotter pin 45 fixedly secures shaft 32 to external actuator means 31, the latter means being responsive, through linkage means not shown, to change in vehicle position. When the vehicle to which switch 10 is attached shifts position relative to a reference plane, external drive lever 31 will be driven to rotate clockwise or counterclockwise. Shaft 32 will then rotate with external drive lever or lever 31 within bushing 37. Spring 26, not being fixedly attached to shaft 32 as cams 30 are, nevertheless tends to rotate with shaft 32 as cams 30, rotating with shaft 32, come to drive against one of the spring 26 extensions 24 as seen in FIG- URES 3A and 3B. The spring 26 is prevented from rotating about shaft 32 by the extension 24 against which cams 30 are not in contact. The latter extension 24 presses against its adjacent arm 18, as seen in FIGURES 3A and 3B, so that a moment exists preventing rotation of spring 26. As cams 30 press further against one of the extensions 24, the arm 18 adjacent thereto is allowed to spring outward as extension 24 yields under the force of rotating cams 30. Separation between stop 21A and arm 18 is now complete. As tilting continues, the outward springing contact arm 18 comes against a stop 47 (a solid fixture welded to casing 12) and the contact elements 21 no longer make contact and switch 10 is open. The amount of rotation by actuator 31 which is needed to achieve this latter total open circuit condition is determined by the spread angle a initially set between cams 30. In FIGURE 2 this angle is shown larger than the angle representation of FIGURES 1B, 3A and 3B and therefore less rotation of lever 31 will achieve the open circuit position using the setting for cams 30 in FIGURE 2 than in FIGURES 1B, 3A and 3B.

Continuing with reference to FIGURES 1A, 1B and 4, a switch 10 vent assembly or vent means 42 is shown attached to casing 12 by convenient means such as bolts 44. The vent assembly 42 comprises a metal baffle plate 46 and block of inert material 50 attached by bolts 44 to casing 12. A vent hole 48 passes through the baffle plate 46 and inert material 50 into the casing 12. The piece of inert material 50, such as plastic or Teflon, is aligned above the vent hole 48 in bafiie plate 46 and held down with the bafile plate 46 to casing 12 by the bolts 44. A maze of passageways 52 through the inert material 50 are provided allowing free air circulation through the vent hole 48 while preventing most solids such as dust particles and sand particles from entering the casing 12. For a dust particle to enter to the interior of casing 12, it would have to achieve four right angle bends through the labyrinth passages 52 in the inert material 50. Since a dust or sand particle has mass and velocity, it is difiicult to see why it should make even one bend through the labyrinth passages 52. Should it enter through the vent hole 48 it will encounter a fiypaper type of trap (not shown) within casing 12. The flypaper trap consists of painting the inside of the casing 12 with a proper paint. The type of paint to be used will have the property of sticking toparticles even when it is dry. The same paint is used as a gasket material for sealing the lid (not shown) of the casing 12. It dries enough to make a seal yet remains soft enough that the lid can be removed when desired.

With further reference to FIGURE 4, the electrical contact arms 18 are described more fully. The contact arms 18 are provided with a general radius bend 19 where bending takes place under actual conditions. Such a general radius increases fatigue life of the members 18. At point 20 the contact arms 18 have a near right angle bend of small radius. The setting of this angle controls the pressure of the contact elements 21 located at the tip of the arms 18. Contact pressures are therefore individually adjustable. As mentioned above, the contact arms 18 are made of spring material, such as beryllium copper, so that they will spring apart when installed unless restraining means are used. No supplementary springs are needed to cause open switch conditions. The contact arms 18 are restrained in the close circuit condition by the extension 24 of spring 26 as seen best in FIGURE 1A. By adopting two spring arms 18 instead of two pivoted levers, pivot friction or possible seizure has been eliminated.

FIGURE 5 presents an alternative embodiment of the teachings of this invention, wherein like components are given like numerals for reference. In FIGURE 5, the actuator assembly 28, casing means 12 and vent assemblies 42 are identical to that in FIGURE 1A. Cam 27 in FIG- URE 5 is bolted to plate 38A which is attached by bolts 40A to casing 12. Cam 27 is actuated to rotate under tilting conditions the same as was cam 30 above. In the vehicle or landing gear truck level condition, cam 27 maintains the spring contact arm 18A in a position such that the switch 60 is electrically closed by contact elements 21 on arm 18A mating with contact elements 21 on arm 18B. Contact arm 18B is rigidly fixed by soldering it to a back plate 38A attached to casing 12 by bolts 33. When the truck tilts, cam 27 is driven to rotate counterclockwise or clockwise by actuator means (not shown) so that cam 27 rides off a contact member 29 on arm 18A leaving the arm 18A free to spring upwards as designated by dashed lines. The new position of arm 18A breaks electrical contact between the contact elements 21 and causes the insulating means 22 to slide across the contact elements 21, wiping contact elements 21 clean. Switch 60 is then in open circuit position.

While in the foregoing there has been shown and described the preferred embodiment of this invention, it is to be understood that minor changes in the details of construction, combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as claimed.

I claim:

1. A vehicle position actuated switch comprising (a) actuator means responsive to change of vehicle position;

(b) a plurality of movable electrical contacts having contact points, means whereby said contacts move relative to one another in response to said actuator means;

(c) insulation means in combination with said plurality of electrical contacts, means whereby when said vehicle tilts, said contact points slide apart on said insulation means to an open switch position, and when said vehicle is restored to its non-tilting position, said contact points slide on said insulation means to make electrical contact.

2. A vehicle position actuated switch comprising (a) actuator means responsive to change of vehicle position;

(b) a plurality of movable electrical contacts having contact points, means whereby said contacts move relative to one another in response to said actuator means;

(c) insulation means in combination with said plurality of electrical contacts, means whereby, when said vehicle tilts said contact points slide apart on said insulation means to an open switch position, and when said vehicle is restored to its non-tilting position said contact points slide on said insulation means to make electrical contact.

(d) container means enclosing said switch and having a vent means allowing for vapor circulation through said container means but preventing entrance of foreign contaminants, having mass, into said container means.

3. The switch defined in claim 2 wherein said vent means comprises an inert material, said inert material defining a maze of passageways interconnecting an open ing, defined by said container means, permitting ventilation into said switch.

References Cited UNITED STATES PATENTS 3,175,059 3/1965 Chesnut ZOO-61.52

ROBERT K. SCHAEFER, Primary Examiner.

MORRIS GINSBURG, A sssistant Examiner. 

1. A VEHICLE POSITION ACTUATED SWITCH COMPRISING (A) ACTUATOR MEANS RESPONSIVE TO CHANGE OF VEHICLE POSITION; (B) A PLURALITY OF MOVABLE ELECTRICAL CONTACTS HAVING CONTACT POINTS, MEANS WHEREBY SAID CONTACTS MOVE RELATIVE TO ONE ANOTHER IN RESPONSE TO SAID ACTUATOR MEANS; (C) INSULATION MEANS IN COMBINATION WITH SAID PLURALITY OF ELECTRICAL CONTACTS, MEANS WHEREBY WHEN SAID VEHICLE TILTS, SAID CONTACT POINTS SLIDE APART ON SAID INSULATION MEANS TO AN OPEN SWITCH POSITION, AND WHEN SAID VEHICLE IS RESTORED TO ITS NON-TILTING POSITION, SAID CONTACT POINTS SLIDE ON SAID INSULATION MEANS TO MAKE ELECTRICAL CONTACT. 